1. Field of the Invention
The present invention relates to controllers for controlling actuators and/or valves. An example of such a controller is a digital valve controller that is programmable and controls an associated valve actuator based on various calibration parameters and input signals. The valve actuator, in turn, controls the position of a valve.
2. Description of Related Art
In conventional valve controllers, repairing a failed loop controller typically requires the normal operation of the valve to be interrupted. For example, the valve would be taken off line or otherwise shut down while its controller is repaired. Repairing the loop controller often involves a recalibration process, which can require fully stroking the valve to properly calibrate the controller. It might be inconvenient at the least, and possibly costly and undesirable, to take the valve off line or shut it down while the controller is repaired. Recalibrating the loop controller can be time consuming and, if done incorrectly, can lead to process control errors and additional down time. If the valve must be fully stroked to properly calibrate the controller, and the controlled process will not permit fully stroking the valve, then the valve must be taken off line so that the controller can be calibrated. It would be useful to provide a valve controller that mitigates one or more of the above shortcomings.